1. Field of the Invention
The present invention relates to connectors for interconnecting optical fibers to each other and to other optical components.
2. Description of the Related Art
Optical fiber communication systems are increasingly being used to transport data in the form of light pulses over long distances because they exhibit a very large capacity for carrying information, are light-weight, and are immune to electromagnetic interference. Important components of any optical fiber communication system are connectors for the optical fibers. These connectors may function as splices for connecting the ends of two optical fibers, or may be used to connect an optical fiber to other optical components.
It is important for the connector to properly align the optical fiber so that the insertion losses are minimized at the point at which the optical fiber is coupled to another optical fiber or to an optical component.
Optical fibers are usually formed of a thin glass or plastic fiber. Accordingly, the connector must also protect the end of the thin fiber from physical damage. In addition, the connector itself must not damage the end of the fiber during the connection or disconnection process.
Prior art connectors typically use a ferrule in which the end of an optical fiber is cemented in place to protect the end of the fiber from physical damage. The ferrule containing the end of the optical fiber is then aligned via insertion of the ferrule into a socket or plug. Because the end of the optical fiber is cemented in the ferrule, the fiber is held at an exact aligned location in the ferrule and the end of the fiber is physically protected.
A typical prior art connector device is disclosed in U.S. Pat. No. 5,768,455 (Konik). This prior art device includes a ferrule 12 for holding a length of bare fiber. The ferrule itself is held in a plug frame 13 (see FIG. 2).
Another prior art connector is shown in U.S. Pat. No. 5,638,474 (Lampert et al.). This prior art connector also employs a ferrule 140 which is held within a base member 150. The ferrule 140 receives the buffered fiber 33 which does not include the outer jacket 31 or strengthening members 32 that are placed over the buffered fiber.
More than one optical fiber may be inserted into a ferrule as shown in the prior art connector of U.S. Pat. No. 5,712,939 (Shahid) and U.S. Pat. No. 5,862,281 (Shahid), in which the fibers are held in place by a mold and the mold is filled with a material that encapsulates the fibers and forms a plug. The encapsulation of the end portions of the fibers is similar to the cementing of the above prior art devices in ferrules. Another prior art connector for holding multiple optical fibers is shown in U.S. Pat. No. 5,625,733 which has a cylindrical ferrule 100, 101 (see FIGS. 1 and 2); this particular connector is specifically designed for connecting optical fibers to optical devices.
The prior art connectors thus far described permanently connect the end of an optical fiber within a ferrule or plug. The Volition fiber optic cable systems manufactured by 3M, on the other hand, comprise plug and socket assemblies for connecting the ends of optical fibers. In the 3M systems the end of the optical fiber is free within the plug and is only held in the plug a preset distance from the end of the fiber. Within the socket, the free end of the plug-carried optical fiber is guided along a V-groove until it abuts the end of the socket-carried optical fiber. The plug and socket are designed so that there is a force urging the optical fibers into abutment when the plug is fully inserted into the socket. A specific type of glass optical fiber is used in this system. In addition, the Volition systems require the use of factory-assembled patch cords.
Accordingly, a significant problem and drawback of these prior art devices is that it is difficult, and in some cases impossible, to field mount the connectors to an optical fiber.